WO2011023587A2

WO2011023587A2 - Use of polyelectrolyte complexes for producing polymer films having oxygen barrier properties

Info

Publication number: WO2011023587A2
Application number: PCT/EP2010/061925
Authority: WO
Inventors: Carmen-Elena Cimpeanu; Thomas Breiner; Dieter Urban; Karl-Heinz Schumacher; Volker Schädler; Heiko Diehl; Hermann Seyffer
Original assignee: Basf Se
Priority date: 2009-08-24
Filing date: 2010-08-17
Publication date: 2011-03-03
Also published as: EP2570196B1; JP2013502337A; EP2570196A2; US20120148855A1; US8980437B2; JP5882209B2; WO2011023587A3; ES2805328T3; EP2473289A2; CN102481597A; CN102481597B; EP2570196A3

Abstract

The invention relates to the use of polyelectrolyte complexes in order to provide an oxygen barrier for packaging materials made of polymer films. Polymer construction components of the polyelectrolyte complex are applied to the polymer film in a polymerized form. The polymer film is coated either with an aqueous dispersion comprising a dispersed polyelectrolyte complex and produced through water-in-water emulsion polymerization, or with a composition comprising a polyelectrolyte complex produced from an anionic polymer and cationic tenside, or the polymer film is coated with at least three alternating layers, wherein one each of two adjacent layers comprises an anionic polyelectrolyte construction component and the other of the two adjacent layers comprises a cationic polyelectrolyte construction component, and polyelectrolyte complexes form on the mutually adjacent boundaries of the alternating layers.

Description

Use of polyelectrolyte complexes for the production of polymer films with oxygen barrier properties

description

The invention relates to the use of polyelectrolyte complexes to impart an oxygen barrier to polymeric film packaging materials. Polymer building components of the polyelectrolyte complex are applied in polymerized form to the polymer film. The polymer film is coated either with an aqueous dispersion containing a dispersed polyelectrolyte complex previously prepared by water-in-water emulsion polymerization or with a composition containing an anionic polymer and cationic surfactant or the polymer film is coated with at least three alternating layers. wherein each one of two adjacent layers contains an anionic polyelectrolyte constituent component and the other of two adjacent layers contains a cationic polyelectrolyte constituent component and polyelectrolyte complexes form at the mutually adjacent interfaces of the alternating layers. When packaging oxidation-sensitive or oxygen-sensitive products, it is important that the packaging materials used have oxygen barrier properties, ie that they have as low a transmission as possible or as low a permeability to oxygen as possible. Since polymer films used as packaging materials, for example of polyolefins such as polyethylene or oriented polypropylene or of polyesters such as polyethylene terephthalate usually in pure, uncoated form show a relatively high permeability to oxygen, various measures have been proposed to the oxygen barrier properties of the packaging materials increase. WO 03/068869 describes a process for the production of packaging materials with oxygen barrier properties, wherein a carrier material is coated with a polymerizable compound and the compound is subsequently polymerized on the carrier material. EP 2 014 730 describes a coating composition for forming a gas barrier film based on a polycarboxylic acid polymer which is crosslinked by means of a zinc compound. WO 07/002322 describes coated polymer films with oxygen barrier properties. The coating composition is a solution of a maleic acid / acrylic acid copolymer and a vinyl alcohol / vinylamine copolymer. After coating, the two copolymers of the coating composition crosslink on the polymer film. WO 98/31719 describes coating compositions for barrier coatings. The compositions contain an ethylenically unsaturated acid monomer and a polyamine containing a built-in crosslinker. After coating, crosslinking takes place by triggering a free-radically induced polymerization. Previously known packaging films with oxygen barrier properties are not yet satisfactory in every respect. Often, oxygen permeabilities are not yet sufficiently low for all applications, or barrier coatings with polymer-based films are not sufficiently flexible. It can then come when kinking or folding in the area of folding to damage the barrier film and consequent insufficient barrier effects.

It was an object of the present invention to provide a further compositions and processes which make it possible to produce packaging with good oxygen barrier properties, in particular in the area of folds, creases and corners. The packaging should be as good as possible temperature-resistant, flexible and block-resistant and as possible no harmful substances such. Contain metals.

The invention relates to the use of at least one polyelectrolyte complex to impart an oxygen barrier to packaging materials made of polymer films, wherein polymer structural components of the polyelectrolyte complex are applied in polymerized form to the polymer film and wherein either at least one polymer film on at least one side with a previously water-in-water emulsion polymerization prepared dispersed polyelectrolyte complex-containing aqueous dispersion or coated with a composition previously prepared from anionic polymer and cationic surfactant polyelectrolyte complex composition; or wherein a polymer film is coated on at least one side with at least three alternating layers, wherein each one of two adjacent layers at least one anionic Polyelektrolytaufbau- component contains and the other of two adjacent layers at least one cationic Polyelektrolytaufbaukomponente and at the mutual, adjacent interfaces of the at least three alternating layers form polyelectrolyte complexes.

The invention also provides a coated polymer film obtainable by use according to the invention, wherein at least one side of the polymer film is coated with at least three alternating layers, one of two adjacent layers containing at least one anionic polyelectrolyte constituent component and the other of two adjacent layers containing at least contains a cationic polyelectrolyte constituent component and forms polyelectrolyte complexes at the mutual, adjacent interfaces of the at least three alternating layers.

The coating prepared according to the invention with the polyelectrolyte complex has oxygen barrier properties. The barrier properties can with the in the Examples of the described permeability test are measured. The term oxygen barrier property means reduced transmission or permeability to oxygen compared to uncoated substrate. The oxygen permeability for polymer films coated according to the invention is preferably less than 30%, in particular less than 20% or less than 10%, for example between 1% and 3% of the value of the uncoated polymer film (measured at 23 ° C. and 0% relative atmospheric humidity).

In one embodiment, the oxygen barrier layer containing the polyelectrolyte complex is provided with moisture protection in order to prevent or at least greatly reduce impairment of the barrier effect due to high atmospheric humidity. The moisture protection can be done by an additional coating with a material which has a barrier effect against water vapor or humidity. Alternatively or cumulatively, a coextrusion with such a material can take place; suitable are, for example, polyolefins, in particular polyethylene. The moisture protection is preferably formed by coating with a polyolefin or by coextrusion of a polyolefin with at least one substance selected from polyelectrolyte complexes, anionic polyelectrolyte constituent components and anionic polyelectrolyte constituent components.

Polyelectrolytes are ionic polymers. Polyelectrolyte complexes in the sense of the invention are the reaction products of oppositely charged ionic polyelectrolyte constituent components, wherein at least one of the synthesis components is a cationic or an anionic polymer. Polyelectrolyte complexes useful in the present invention are e.g. formed from an anionic polymer and from a cationic polymer or from an anionic polymer and from a non-polymeric, cationic surfactant, or from a cationic polymer and from a non-polymeric, anionic surfactant. Preference is given to polyelectrolyte complexes of cationic polymer and anionic polymer or of an anionic polymer and non-polymeric, cationic surfactant. As a rule, the polyelectrolyte complexes have a defined stoichiometric composition, i. the equivalent ratio of anionic and cationic groups in these complexes is at or near 1. However, the polyelectrolyte complexes can also be predominantly anionic or predominantly cationically charged. According to the invention, in addition to such polyelectrolyte complexes, a cationic or an anionic polymer may additionally be present in excess, i. be present in free, uncomplexed form.

In one embodiment of the invention, aqueous dispersions of polyelectrolyte complexes are used. These polyelectrolyte dispersions can be prepared by so-called water-in-water emulsion polymerization. These are ionically stabilized, homogeneously dispersed complexes of anionic polymer and of cationic polymer. The polyelectrolyte complexes are preferably based on the incorporated monomers predominantly cationically charged at low pH. The dispersions can be obtained by free radical polymerization of ethylenically unsaturated anionic monomers in an aqueous medium in the presence of at least one cationic polymer at a suitable pH. In one embodiment, the anionic monomers are used in an amount such that the number of anionic groups in the anionic monomers falls below the number of cationic groups in the cationic polymers by at least 1 mol%, measured at pH 2.7 and 20 ⁰ C. A suitable production process is described, for example, in DE 10 2005 007 483.

The amount of cationic polymer used to prepare the dispersed polyelectrolyte complex is preferably selected such that, for example, up to 150 mol% or more per mole of the cationic groups of the cationic polymer or in the total amount of cationic monomers used in the polymerization up to 100 mol%, preferably 1 to 99 mol% or 10 to 80 mol% of anionic groups of at least one anionic polymer, measured at pH 2.7 and 20 ^° C. The polyelectrolyte complexes formed with less than 100 mol% of anionic groups are predominantly cationically charged at pH 2.7 and 20 ° C. Anionic polymers are polymers with anionic groups, in particular organic polymers with carboxylate, phosphate or sulfate groups. It is also possible to use the corresponding acids, provided that they are either neutralized by bases present in the reaction medium or converted into anionic groups by basic groups of the cationic polymer. Examples of suitable anionic polymers are those formed by free-radical polymerization of ethylenically unsaturated, radically polymerizable anionic polymers. Also included are copolymers of at least one anionic monomer and one or more different nonionic copolymerizable monomers. Examples of suitable ethylenically unsaturated anionic monomers are monoethylenically unsaturated C.sub.3- to C.sub.10- or C.sub.3- to C.sub.-carboxylic acids, such as acrylic acid, methacrylic acid, ethacrylic acid, crotonic acid, maleic acid, fumaric acid, vinylsulfonic acid, styrenesulfonic acid, acrylamidomethylpropanesulfonic acid, vinylphosphonic acid, itaconic acid and the alkali metal, alkaline earth metal or ammonium salts of these acids into consideration. Preferred anionic monomers include acrylic acid, methacrylic acid, maleic acid and 2-acrylamido-2-methylpropanesulfonic acid. Particularly preferred are aqueous dispersions of polymers based on acrylic acid. The anionic monomers can be polymerized either alone to form homopolymers or else mixed with one another to give copolymers. Examples include the homopolymers of acrylic acid, homopolymers of methacrylic acid or copolymers of acrylic acid and maleic acid, copolymers of acrylic acid and methacrylic acid and copolymers of methacrylic acid and maleic acid. However, the polymerization of the anionic monomers can also be carried out in the presence of at least one other ethylenically unsaturated monomer. These monomers may be nonionic or may carry a cationic charge. Examples of nonionic comonomers are acrylamide, methacrylamide, N-Cr to C3-alkylacrylamides, N-vinylformamide, acrylic esters of monohydric alcohols having 1 to 20 C atoms, in particular methyl acrylate, ethyl acrylate, isobutyl acrylate and n-butyl acrylate, methacrylic acid esters of monohydric alcohols with 1 up to 20 carbon atoms, for example methyl methacrylate and ethyl methacrylate, and also vinyl acetate and vinyl propionate.

Suitable cationic monomers which can be copolymerized with the anionic monomers are dialkylaminoethyl acrylates, dialkylaminoethyl methacrylates, dialkylaminopropyl acrylates, dialkylaminopropyl methacrylates, dialkylaminoethylacrylamides, dialkylaminoethylmethacrylamides, dialkylaminopropylacrylamides, dialkylaminopropylmethacrylamides, diallyldimethylammonium chloride, vinylimidazole and also the basic monomers neutralized and / or quenched with acids , Specific examples of cationic monomers are dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate, diethylaminoethyl acrylate, diethylaminoethyl methacrylate, dimethylaminopropyl acrylate, dimethylaminopropyl methacrylate, diethylaminopropyl acrylate and diethylaminopropyl methacrylate, dimethylaminoethylacrylamide, dimethylaminoethylmethacrylamide, dimethylaminopropylacrylamide, dimethylaminopropylmethacrylamide, diethylaminoethylacrylamide and diethylaminopropylacrylamide.

The basic monomers may be completely or even partially neutralized or quaternized, for example, in each case from 1 to 99%. Preferred quaternizing agent for the basic monomers is dimethylsulfate. However, the quaternization of the monomers can also be carried out with diethyl sulfate or with alkyl halides such as methyl chloride, ethyl chloride or benzyl chloride. The cationic monomers are used most in an amount such that the resulting polyelectrolyte lytkomplexe total at pH values <6.0 and carry a temperature of 20 ⁰ C an anionic charge. The anionic excess charge in the resulting amphoteric polymers is, for example, at least 5 mol%, preferably at least 10 mol%. The comonomers are used in the preparation of the anionic polyelectrolyte complexes, for example in amounts such that the resulting polymer dispersions when diluted with water and at pH values above 7.0 and a temperature of 20 ⁰ C are water-soluble and have an anionic charge. Based on the total monomers used in the polymerization, the amount of nonionic and / or cationic comonomers is, for example, 0 to 99, preferably 5 to 75 wt .-% and is usually in the range of 5 to 25 wt .-%. Examples of preferred copolymers are copolymers of 25 to 90% by weight of acrylic acid and 75 to 10% by weight of acrylamide. Preferably, at least one ethylenically unsaturated C3 to C5 carboxylic acid is polymerized in the absence of other monoethylenically unsaturated monomers. Particular preference is given to homopolymers of acrylic acid obtainable by free-radical polymerization of acrylic acid in the absence of other monomers.

In one embodiment, the anionic polymer contains 2-acrylamido-2-methylpropanesulfonic acid (AMPS). Preferably, acrylic acid is copolymerized with AMPS. The amount of AMPS can be, for example, from 0.1 to 15 mol% or from 0.5 to 10 mol%, based on the amount of all monomers.

The polymerization can additionally be carried out in the presence of at least one crosslinker. Copolymers having a higher molecular weight are then obtained than when the anionic monomers are polymerized in the absence of a crosslinking agent. Incorporation of a crosslinker in the polymers also results in reduced solubility of the polymers in water. Depending on the amount of copolymerized crosslinker, the polymers become water-insoluble, but are swellable in water. Crosslinkers which can be used are all compounds which have at least two ethylenically unsaturated double bonds in the molecule. Examples of crosslinkers are triallylamine, pentaerythritol triallyl ether, pentaerythritol tetraallyl ether, methylenebisacrylamide, N, N'-divinylethyleneurea, allyl ethers containing at least two allyl groups or vinyl ethers of polyhydric alcohols containing at least two vinyl groups, such as, for example, Sorbitol, 1, 2-ethanediol, 1, 4-butanediol, trimethylolpropane, glycerol, diethylene glycol and of sugars such as sucrose, glucose, mannose, fully esterified with acrylic acid or methacrylic dihydric alcohols having 2 to 4 carbon atoms such as ethylene glycol dimethacrylate, ethylene glycol diacrylate , Butanediol dimethacrylate, butanediol diacrylate, diacrylates or dimethacrylates of polyethylene glycols having molecular weights of 300 to 600, ethoxylated trimethylenepropane triacrylates or ethoxylated trimethylenepropane trimethacrylates, 2,2-bis (hydroxymethyl) butanol trimethacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate and triallylmethylammonium chloride. If crosslinking agents are used in the preparation of the dispersions according to the invention, the amounts of crosslinker used in each case are, for example, 0.0005 to 5.0, preferably 0.001 to 1.0,% by weight, based on the total monomers used in the polymerization , Preferred crosslinkers are

Pentaerythritol triallyl ether, pentaerythritol tetraallyl ether, N, ^{N'-divinylethyleneurea,} at least two allyl groups-containing allyl ethers of sugars such as sucrose, glucose or mannose, and triallylamine and mixtures of these compounds. If the polymerization of at least one anionic monomer is carried out in the presence of at least one crosslinking agent, crosslinked copolymers of acrylic acid and / or methacrylic acid are preferably prepared by reacting acrylic acid and / or methacrylic acid in the presence of pentaerythrityl triallyl ether, pentaerythritol tetraallyl ether, N, ^{N'-divinylethyleneurea,} at least two allyl groups-containing allyl ethers of sugars such as sucrose, glucose or mannose, or triallylamine and also mixtures of these compounds polymerized. Depending on the amounts of crosslinkers used in the polymerization, the resulting polyelectrolyte complexes are soluble or swellable in dilute aqueous solution at pH values> 7.0.

The cationic polymers used for forming the polyelectrolyte complexes are preferably water soluble, meaning they have a solubility in water of at least 1 g / l at 20 ⁰ C. Cationic polymers are polymers with cationic groups, in particular organic polymers with quaternary ammonium groups. It is also possible to use polymers having primary, secondary or tertiary amine groups, provided that they are either protonated by acids contained in the reaction medium or by acid groups of the anionic polymer and thus converted into cationic groups. The amine or ammonium groups of the cationic polymer can be present as substituents or as part of the polymer chain. They may also be part of an aromatic or non-aromatic ring system.

Suitable cationic polymers are e.g. Polymers from the group of

(a) polymers containing vinylimidazolium units,

(b) polydiallyldimethylammonium halides,

(c) polymers containing vinylamine units,

(d) polymers containing ethyleneimine units,

(e) polymers containing dialkylaminoalkyl acrylate and / or dialkylaminoalkyl methacrylate units and

(f) polymers containing dialkylaminoalkylacrylamide and / or dialkylaminoalkylmethacrylamide units.

Examples of cationic polymers are

(a) homopolymers of vinylimidazolium methosulfate and / or copolymers of vinylimidazolium methosulfate and N-vinylpyrrolidone,

(b) polydiallyldimethylammonium chlorides,

(c) polyvinylamines,

(d) polyethyleneimines

(e) polydimethylaminoethyl acrylate, polydimethylaminoethyl methacrylate, copolymers of acrylamide and dimethylaminoethyl acrylate and copolymers of acrylamide and dimethylaminoethyl methacrylate, where the basic monomers may also be present in the form of the salts with mineral acids or in quaternized form, and

(f) polydimethylaminoethylacrylamide, polydimethylaminoethylmethacrylamide and copolymers of acrylamide and dimethylaminoethylacrylamide. The basic monomers can also be present in the form of the salts with mineral acids or in quaternized form. The average molecular weights M _{w of} the cationic polymers are at least 500. They are for example in the range of 500 to 1 million, preferably from 1,000 to 500,000 or 2,000 to 100,000.

Preferably used as cationic polymers

(a) homopolymers of vinylimidazolium methosulfate and / or copolymers of vinylimidazolium methosulfate and N-vinylpyrrolidone having an average molecular weight Mw of in each case 500 to 500,000,

(b) polydiallyldimethylammonium chlorides having an average molecular weight M _{w of} from 1000 to 500,000,

(c) polyvinylamines having an average molecular weight M _w of 500 to 1 million and

(d) Polyethyleneimines having an average molecular weight M _w of 500 to 1 million. The copolymers of vinylimidazolium methosulfate and N-vinylpyrrolidone listed under (a) contain, for example, 10 to 90% by weight of N-vinylpyrrolidone polymerized. Instead of N-vinylpyrrolidone can be used as comonomer at least one compound from the group of ethylenically unsaturated C3 to Cs carboxylic acids such as acrylic acid or methacrylic acid or esters of these carboxylic acids with 1 to 18 carbon atoms containing monohydric alcohols such as methyl acrylate, ethyl acrylate , Isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, methyl methacrylate, ethyl methacrylate or n-butyl methacrylate.

Polymers of group (b) are preferably polydiallyldimethylammonium chloride. Also suitable are copolymers of diallyldimethylammonium chloride and dimethylaminoethyl acrylate, copolymers of diallyldimethylammonium chloride and dimethylaminoethyl methacrylate, copolymers of diallyldimethylammonium chloride and diethylaminoethyl acrylate, copolymers of diallyldimethylammonium chloride and dimethylaminopropyl acrylate, copolymers of dialkyldimethylammonium chloride and dimethylaminoethylacrylamide and copolymers of diallyldimethylammonium chloride and dimethylaminopropylacrylamide. The copolymers of diallyldimethylammonium chloride contain, for example, from 1 to 50, usually from 2 to 30, mol% of at least one of the abovementioned comonomers in copolymerized form. Vinylamine-containing polymers (c) are obtainable by polymerizing N-vinylformamide optionally in the presence of comonomers and hydrolysing the vinylformamide polymers with elimination of formyl groups to form amino groups. The degree of hydrolysis of the polymers may be, for example, 1 to 100%, and most often in the range of 60 to 100%. The average molecular weights M _w are up to 1 million. Polymers containing vinylamine units are marketed, for example, as Catiofast® grades by BASF SE. Ethylenimine units containing polymers of group (d) such as polyethyleneimines are also commercial products. They are sold, for example, under the name Polymin® by BASF SE, for example Polymin® SK. These cationic polymers are polymers of ethyleneimine prepared by polymerizing ethyleneimine in an aqueous medium in the presence of small amounts of acids or acid-forming compounds such as halogenated hydrocarbons such as chloroform, carbon tetrachloride, tetrachloroethane or ethyl chloride, or condensation products of epichlorohydrin and amino group-containing compounds such as mono- and polyamines, for example dimethylamine, diethylamine, ethylenediamine, diethylenetriamine and triethylenetetramine or ammonia. They have, for example, molar masses M _w of 500 to 1 million, preferably 1000 to 500,000.

This group of cationic polymers also includes graft polymers of ethyleneimine on compounds having a primary or secondary amino group, e.g. Polyamidoamines from dicarboxylic acids and polyamines. If appropriate, the polyamidoamines grafted with ethyleneimine can also be reacted with bifunctional crosslinkers, for example with epichlorohydrin or bis-chlorohydrin ethers of polyalkylene glycols. Suitable cationic polymers of group (e) are polymers containing dialkylaminoalkyl acrylate and / or dialkylaminoalkyl methacrylate units. These monomers may be used in the form of the free bases, but preferably in the form of the salts with mineral acids such as hydrochloric acid, sulfuric acid or phosphoric acid and in quaternized form in the polymerization. Suitable quaternizing agents are, for example, dimethyl sulfate, diethyl sulfate, methyl chloride, ethyl chloride, cetyl chloride or benzyl chloride. Both homopolymers and copolymers can be prepared from these monomers. Suitable comonomers are, for example, acrylamide, methacrylamide, N-vinylformamide, N-vinylpyrrolidone, methyl acrylate, ethyl acrylate, methyl methacrylate and mixtures of the stated monomers.

Cationic polymers of group (f) are dimethylaminoethylacrylamide or dimethylaminoethyl methacrylamide units containing polymers which contain the basic monomers preferably in the form of salts with mineral acids or in quaternized form. These may be homopolymers and copolymers. Examples are homopolymers of dimethylaminoethylacrylamide which is completely quaternized with dimethyl sulfate or with benzyl chloride, homopolymers of dimethylaminoethylmethacrylamide which is completely quaternized with dimethyl sulfate, methyl chloride, ethyl chloride or benzyl chloride, and also copolymers of acrylamide and dimethylaminoethylacrylamide quaternized with dimethyl sulfate.

In the preparation of the aqueous dispersions according to the invention, the following cationic polymers are preferably used: (a) homopolymers of vinylimidazolium methosulfate and / or copolymers of vinylimidazolium methosulfate and N-vinylpyrrolidone having an average molecular weight Mw of from 1,000 to 100,000,

(b) polydiallyldimethylammonium chlorides having an average molecular weight M _{w of} from 2,000 to 100,000 and / or

(C) Polyvinylamines having an average molecular weight M _w of 1000 to 500 000. The polyvinylamines are preferably used in the form of salts with sulfuric acid or hydrochloric acid. Apart from those polymers which are composed solely of cationic monomers, it is also possible to use amphoteric polymers as cationic polymers, provided that they carry a total cationic charge. The cationic excess charge in the amphoteric polymers is for example at least 5 mol%, preferably at least 10 mol%, and is usually in the range from 15 to 95 mol%. Examples of amphoteric polymers with a cationic excess charge are

Copolymers of acrylamide, dimethylaminoethyl acrylate and acrylic acid which contain at least 5 mol% more dimethylaminoethyl acrylate as copolymerized with acrylic acid;

- Copolymers of vinylimidazolium methosulfate, N-vinylpyrrolidone and acrylic acid containing polymerized at least 5 mol% more Vinylimidazoliummethosulfat than acrylic acid polymerized;

hydrolyzed copolymers of N-vinylformamide and an ethylenically unsaturated C3 to Cδ carboxylic acid, preferably acrylic acid or methacrylic acid, with at least 5 mol% higher vinylamine units than units of ethylenically unsaturated carboxylic acids;

Copolymers of vinylimidazole, acrylamide and acrylic acid, wherein the pH is selected so that at least 5 mol% more vinylimidazole is cationically charged when acrylic acid is copolymerized.

Aqueous dispersions of polyelectrolyte complexes can be prepared by free-radically polymerizing the anionic monomers in question, if appropriate in the presence of other monomers, in an aqueous medium in the presence of cationic polymers. The amount of basic or cationic monomers can be chosen such that the resulting polymer complexes always carry an excess of anionic charge, determined at pH 7 and 20 ^° C. The determination of the charge density of the polyelectrolytes or polyelectrolyte complexes can be carried out according to D. Hörn, Progr. Colloid & Polymer Sci., Vol. 65, 251-264 (1978). Basic polymers are preferably used in the form of the salts with mineral acids or organic acids such as formic acid or acetic acid in the polymerization. puts. Otherwise, these salts form anyway in the polymerization, because the polymerization is carried out at a pH <6.0.

The aqueous dispersions of predominantly anionically charged polyelectrolyte complexes which are preferred according to the invention can be prepared by free-radical polymerization of ethylenically unsaturated anionic monomers in aqueous medium in the presence of at least one water-soluble cationic polymer, preferably 0.5 g per mole of the anionic monomers used in the polymerization to 49 mol% of at least one cationic polymer. The polymerization is carried out in aqueous medium at a pH below 6, e.g. in the range of 0 to 5.9, preferably 1 to 5 and in particular of 1, 5 to 3. The pH in question is usually obtained by using acid group-containing polymers in the form of free acid groups in the polymerization. The pH can be varied by adding a base such as in particular aqueous sodium hydroxide solution or potassium hydroxide solution for the partial neutralization of the acid groups of the anionic monomers in the stated range. However, if one starts from alkali metal, alkaline earth metal or ammonium salts of anionic monomers, is added either a mineral acid or an organic acid such as formic acid, acetic acid or propionic acid to adjust the pH.

If appropriate, the polymerization can additionally be carried out in the presence of at least one chain transfer agent. This gives polymers which have a lower molecular weight than polymers prepared without chain transfer agents. Examples of chain transfer agents are organic compounds which contain sulfur in bonded form, such as dodecylmercaptan, thiodiglycol, ethylthioethanol, di-n-butylsulfide, di-n-octylsulfide, diphenylsulfide, diisopropyl disulfide, 2-mercaptoethanol, 1,3-mercaptopropanol, 3-mercaptopropane-1, 2-diol, 1, 4-mercaptobutanol, thioglycolic acid, 3-mercaptopropionic acid, mercaptosuccinic acid, thioacetic acid and thiourea, aldehydes, organic acids such as formic acid, sodium formate or ammonium formate, alcohols such as in particular isopropanol and phosphorus compounds, eg

Sodium. One can use a single or several chain transfer agents in the polymerization. If used in the polymerization, they are used, for example, in an amount of 0.01 to 5.0, preferably 0.2 to 1 wt .-%, based on the total monomers, a. The chain transfer agents are preferably used together with at least one crosslinker in the polymerization. By varying the amount and the ratio of chain transfer agent and crosslinker, it is possible to control the rheology of the resulting polymers. Chain transfer agents and / or crosslinkers may be initially charged in the polymerization, for example, in the aqueous polymerization medium or dosed together or separately from the monomers, depending on the progress of the polymerization, to the polymerization batch. The polymerization usually uses initiators which form radicals under the reaction conditions. Suitable polymerization initiators are, for example, peroxides, hydroperoxides, hydrogen peroxide, sodium or potassium persulfate, redox catalysts and azo compounds such as 2,2-azobis (N, N-dimethyleneisobutyricin) dihydrochloride, 2,2-azobis (4-methoxy-2,4-dimethylvaleronitrile ), 2,2-azobis (2,4-dimethylvaleronitrile) and 2,2-azobis (2-amidinopropane) dihydrochloride. The initiators are used in the amounts customary in the polymerization. Preferably, azo initiators are used as polymerization initiators. However, it is also possible to initiate the polymerization by means of high-energy rays such as electron beams or by irradiation with UV light.

The polymerization of the anionic monomers is carried out, for example, batchwise by initially introducing the monomers and at least one cationic compound in a polymerization zone and metering the polymerization initiator in portions or continuously. However, preference is given to a semicontinuous procedure in which water and polymerization initiator are initially introduced and at least one anionic monomer and at least one cationic polymer are metered continuously under polymerization conditions. However, it is also possible to introduce the initiator into the polymerization zone continuously or in portions, but separately from the monomer feed and the metering of cationic polymer. It is also possible to initially introduce some of the monomers, for example 5 to 10% by weight, together with a corresponding fraction of at least one cationic polymer in a polymerization zone, to start the polymerization in the presence of an initiator and to leave the remaining part of the monomers, the cationic polymer and the initiator continuously or in portions added. The polymerization is usually carried out in all cases with the exclusion of oxygen under an inert gas atmosphere, for example under nitrogen or helium. The polymerization temperatures are for example in the range of 5 to 100 ⁰ C, preferably 15 to 90 ⁰ C and usually at 20 to 70 ⁰ C. The polymerization temperature depends very much on the particular initiator which is used.

The concentration of the polyelectrolyte complexes in the solutions or aqueous dispersions used for the coating, in particular the aqueous dispersions prepared by water-in-water emulsion polymerization, is preferably at least 1% by weight, in particular at least 5% by weight and up to 50 or up to 60 wt.%. In most cases, the content of polyelectrolyte complexes in the aqueous dispersion is from 1 to 40% by weight or from 5 to 35% by weight, in particular from 15 to 30% by weight. Preferred aqueous dispersions of the polyelectrolyte complexes have a viscosity of 100 to 150,000 mPas, or 200 to 5,000 mPas (measured with a Brookfield viscometer at pH values below 6.0 and a temperature of 20 ^° C. 20 ° C, 20 rpm, spindle 4). Depending on the polymerization conditions and the particular monomers used or combinations of monomers and auxiliaries such as chain transfer agents, the polyelectrolyte complexes have different molecular weights. The average molecular weight M _{w of} the polyelectrolyte complexes is, for example, 1,000 to 10 million, preferably 5,000 to 5 million, and is usually in the range of 10,000 to 3 million. The molecular weight is determined with the aid of light scattering. The average particle size of the dispersed polyelectrolyte complexes is, for example, 0.1 to 200 μm, preferably 0.5 to 70 μm. You can z. B. with the help of optical microscopy, light scattering or freeze-fracture electron microscopy are determined.

Embodiments of the invention are in particular the use of polyelectrolyte complexes formed from

^* Homopolymers of acrylic acid and polymethyl vinylimidazolium containing reindeer;

^* Homopolymers of acrylic acid and homopolymers having vinylimidazolium;

^* Homopolymers of acrylic acid and copolymers of monomers with vinylimidazolium units and vinyllactams, in particular vinylpyrrolidone;

^* Copolymers of acrylic acid with 2-acrylamido-2-methyl-propanesulfonic acid and vinylidene limidazoliumeinheiten containing polymers;

^* Copolymers of acrylic acid with 2-acrylamido-2-methylpropanesulfonic acid and homopolymers with vinylimidazolium units;

^* Copolymers of acrylic acid with 2-acrylamido-2-methylpropanesulfonic acid and copolymers of monomers with vinylimidazolium units and vinyllactams, in particular vinylpyrrolidone.

In one embodiment of the invention, the coating of the polymer films takes place with a composition comprising a polyelectrolyte complex previously prepared from anionic polymer and cationic surfactant. Suitable anionic polymers are those mentioned above, preferred anionic polymers are composed of acrylic acid or methacrylic acid as single monomers or as monomers besides nonionic comonomers, e.g. Polyacrylates, synthesized from acrylic acid or methacrylic acid and acrylic acid or methacrylic acid esters of monohydric alcohols having 1 to 20, preferably 1 to 12 carbon atoms. Suitable cationic surfactants are non-polymeric substances which are both cationic or cationizable

Group, in particular a protonated amine group or preferably a quaternary ammonium group and a hydrophilic group, for example an alkyl or aryl group having at least 6 carbon atoms. Preferred cationic surfactants are surfactants containing a quaternary ammonium group, e.g. those of the general formula

NMR ¹ R ² R ³ R ⁴ XH where R 1 to R 4 independently of one another are aliphatic groups, aromatic groups, alkoxy groups, polyoxyalkylene groups, alkylamido groups, hydroxyalkyl groups, aryl groups or alkaryl groups each having 1 to 22 C atoms, in each case at least one of the radicals R 1 to R 4 having at least 8 C atoms and X "represents an anion, for example a halogen, acetate, phosphate, nitrate or alkyl sulfate, preferably a chloride The aliphatic groups may also contain, in addition to the C atoms and the hydrogen atoms, cross-links or other groups such as further amino groups suitable cationic surfactants are the chlorides or bromides of alkyldimethylbenzylammonium salts, alkyltrimethylammonium salts, for example cetyltrimethylammonium chloride or bromide, tetradecyltrimethylammonium chloride or bromide, alkyldimethylhydroxyethylammonium chlorides or bromides, the dialkyldimethylammonium chlorides or bromides, alkylpyridinium ze, for example lauryl or cetylpyridinium chloride, alkylamino-ethyltrimethylammonium ether sulfates and compounds having a cationic character such as amine oxides, for example alkylmethylamine oxides or alkylaminoethyl-dimethylamine oxides. Particularly preferred is cetyltrimethylammonium chloride.

In one embodiment of the invention, a polymer film is coated on at least one side with at least three alternating layers, wherein in each case one of two adjacent layers contains at least one anionic Polyelektrolytaufbaukompo- nent and the other of two adjacent layers at least one cationic Polyelektrolytaufbaukomponente contains and to the mutual , adjacent interfaces of the at least three alternating layers can form polyelectrolyte complexes. The combination of first to third coating of the polymer film imparts oxygen barrier properties.

The coating with at least three alternating layers is preferably carried out in that

(a1) the polymer film is provided on at least one side with a first coating which contains at least one anionic polymer,

(b1) providing the first coating with a second coating containing at least one cationic substance selected from cationic surfactants and cationic polymers, and

(c1) providing the second coating with a third coating containing at least one anionic polymer; or that

(a2) the polymer film is provided on at least one side with a first coating which contains at least one cationic substance selected from cationic surfactants and cationic polymers,

(b2) providing the first coating with a second coating containing at least one anionic polymer, and (c2) providing the second coating with a third coating containing at least one cationic substance selected from cationic surfactants and cationic polymers. As anionic polymers, cationic polymers and cationic surfactants, the above-mentioned Polyelektrolytaufbaukomponenten can be used. Preferably, a sandwich structure of three layers, wherein the outer layers each contain at least one same or different anionic polymer and the middle layer contains at least one cationic polymer. Anionic polymers are in particular olefin / (meth) acrylic acid copolymers. Cationic polymers are in particular polyvinylamines or completely or partially hydrolyzed polyvinylformamides.

Anionic polyelectrolyte constituent components which are suitable for all embodiments are, in particular, anionic polymers which can be prepared from monomers selected from the group consisting of monoethylenically unsaturated C 3 - to C 10 -carboxylic acids, vinylsulfonic acid, styrenesulfonic acid, acrylamidomethylpropanesulfonic acid, vinylphosphonic acid and salts of these acids. Cationic polyelectrolyte constituent components which are suitable for all embodiments are, in particular, cationic polymers selected from the group consisting of polymers containing vinylimidazolium units, polydiallyldimethylammonium halides, polymers comprising ethyleneamine units, polymers containing ethyleneimine units, polymers containing dialkylaminoalkylacrylate units, polymers containing dialkylaminoalkylacrylate units, dialkylaminoalkylacrylamide units containing polymers and dialkylaminoalkylmethacrylates. amide units containing polymers or cationic surfactants selected from the group consisting of compounds of the general formula

NMR ¹ R ² R ³ R ⁴ XH

where R 1 to R 4 independently of one another are alkyl groups each having 1 to 22 C atoms, where in each case at least one of the radicals R 1 to R 4 has at least 8 C atoms and X represents an anion, for example a halogen, acetate, phosphate, nitrate or A preferred combination, in particular for embodiments with alternating layers, is the combination of one or more completely or partially hydrolyzed polyvinylformamides with one or more homopolymers or copolymers of acrylic acid or methacrylic acid Foil substrates with an aqueous solution or dispersion of at least one polyelectrolyte complex or at least one structural component coated a polyelectrolyte complex. Suitable substrates are in particular polymer films. The solutions or dispersions used for the coating may contain further additives or auxiliaries, for example thickeners for adjusting the rheology, wetting aids or binders.

Polymer films preferred as carrier material are films of oriented polypropylene or polyethylene, which polyethylene may have been prepared by both high pressure and low pressure polymerization of ethylene. Other suitable carrier films are, for example, films of polyester, such as polyethylene terephthalate, films of polyamide, polystyrene and polyvinyl chloride. In one embodiment, the support material is biodegradable films, e.g. from biodegradable aliphatic-aromatic copolyesters and / or polylactic acid, for example Ecoflex® or Ecovio® films. Suitable copolyesters are e.g. formed from alkanediols, in particular C 2 to C 8 alkanediols, e.g. 1, 4-butanediol, from aliphatic dicarboxylic acids, in particular C 2 to C 8

Dicarboxylic acids such as e.g. Adipic acid and from aromatic dicarboxylic acids such as e.g. Terephthalic acid.

The thickness of the carrier films is generally in the range of 10 to 200 microns, in films of polyamide at 30 to 50 microns, in films of polyethylene terephthalate at 10 to 40 microns, in films of polyvinyl chloride at about 100 microns and films of polystyrene at about 30-75 microns.

The application can be carried out, for example, on coating machines in such a way that the coating composition is applied to a carrier film made of a plastic. If web-shaped materials are used, the polymer dispersion is usually applied from a trough over an applicator roll and leveled with the aid of an air brush. Other ways of applying the coating succeed, for example. with the aid of the reverse gravure method, with a spray method or with a roller blade or with other coating methods known to the person skilled in the art.

Apart from these coating methods, the gravure and high-pressure methods known from printing technology are likewise suitable for the production of a barrier coating by means of a polyelectrolyte complex. Instead of different colors in the

Color printing stations are here, for example, the different polymers applied alternately by print job. The printing process to be mentioned is the film printing process known to the person skilled in the art as a high-pressure process, the gravure process as an example of intaglio printing, and offset printing as an example of lithographic printing. You can also use modern digital printing, printing by inkjet, electrophotography or direct imaging. In one embodiment, the polyelectrolyte complex is first formed in situ on the packaging material by applying two, three or more coating compositions simultaneously or in one step immediately after one another, for example by a cascade coating, wherein one of the coating compositions contains at least one anionic polymer and the other coating composition contains at least one cationic polymer. It is preferred that first at least a first coating composition is applied, which contains at least one cationic polymer having primary, secondary or tertiary amine groups and then at least one second coating composition is applied, which contains at least one anionic polymer having acid groups. The cationic polymers having amino groups are, for example, polymers having units selected from the group consisting of vinylamine, ethyleneimine, dialkylaminoalkyl acrylate, dialkylaminoalkyl methacrylate, dialkylaminoalkylacrylamide, dialkylaminoalkylmethacrylamide and mixtures thereof; in particular polyvinylamines, polyethyleneimines, polydimethylaminoethyl acrylate, polydimethylaminoethyl methacrylate, copolymers of acrylamide and dimethylaminoethyl acrylate and copolymers of acrylamide and dimethylaminoethyl methacrylate. The anionic polymers having acid groups are, for example, polymers having units selected from acrylic acid, methacrylic acid, maleic acid, 2-acrylamido-2-methylpropanesulfonic acid and mixtures thereof, in particular homopolymers of acrylic acid and copolymers of acrylic acid and 2-acrylamido-2-methylpropanesulfonic acid.

In order to improve the adhesion to a film even further, the carrier film may be previously subjected to a corona treatment. The amounts applied to the sheet-like materials are, for example, preferably 1 to 10 g (polymer, solids) per m ² , preferably 2 to 7 g / m ² for films, or preferably 10 to 30 g / m ² for paper or board. After the application of the polyelectrolyte complexes on the flat substrates, the solvent is evaporated. For this purpose, for example, when working continuously, the material may pass through a dryer channel which may be equipped with an infrared radiation device. Thereafter, the coated and dried material is passed over a cooling roll and finally wound up. The thickness of the dried coating is preferably 0.5 to 50 μm, more preferably 2 to 20 μm.

The coated with the polyelectrolyte complex substrates show excellent barrier to oxygen, especially in wrinkles, folds and corners. The coated substrates can be used as such as packaging, preferably for food. The coatings have very good mechanical properties and show, for example, good blocking behavior and essentially no crack formation. In order to obtain special surface or coating properties of the packaging materials, for example a good printability, even better sealing and blocking behavior, good water resistance, it may be advantageous to coat the coated substrates with cover layers which additionally provide these desired properties. The substrates precoated with polyelectrolyte complexes show good overcoatability. It can be overcoated again according to a method mentioned above or coated several times in a continuous process without intermediate winding and unwinding of the film. The oxygen barrier layer is thereby inside the system, the surface properties are then determined by the cover layer. The cover layer has good adhesion to the fat barrier layer. Particularly preferred is the application of a moisture protection coating, which ensures the effectiveness of the oxygen barrier layer even at higher humidities. Examples

Measurement of the oxygen barrier effect:

The oxygen transmission or the oxygen permeability was determined on coatings on polymer films at the respectively indicated relative humidity. Initially, the oxygen transmission (transmission) is measured, which is then converted to a layer thickness of 1 micron and given as oxygen permeability with the unit cm ³ (1 micron) / (m ² xdx bar), where d is the time in days. The determination is based on ASTM-D 3985. Example 1: Three-layer barrier

Slide A (comparison):

Polyethylene terephthalate polymer film having a thickness of 25 μm

Slide B (comparison):

A polymer film of polyethylene terephthalate having a thickness of 25 μm was coated with a layer of 10 parts by weight of ethylene / methacrylic acid copolymer and 90 parts by weight of poly (ethyl acrylate) having a thickness of 13 μm.

Film C (according to the invention):

A polymer film of polyethylene terephthalate having a thickness of 25 μm was coated with a first layer of 10 parts by weight of ethylene / methacrylic acid copolymer and 90 parts by weight of poly (ethyl acrylate) having a thickness of 8 μm. Subsequently, a second layer of polyvinylamine (more than 95% hydrolysed poly (N-vinylformamide) of a thickness of 4 microns was coated, finally again with a layer of 10 parts by weight of ethylene / methacrylic acid copolymer and 90 parts by weight of poly (ethyl acrylate) of a thickness coated at 8 μm (third layer), forming at the interfaces between first and second and between second and third layers polyelectrolyte complexes. The oxygen barrier effect was measured at 0% relative humidity.

Oxygen transmission film A: 70 cm ³ / (m ² xd)

Oxygen transmission film B: 90 cm ³ / (m ² xd)

Oxygen transmission film C: 3 cm ³ / (m ² xd)

Oxygen permeability Film C: 60 cm ³ (1 μm) / (m ² xdx bar) Example 2

A polymer film of oPP (oriented polypropylene) having a thickness of 30 μm was coated with a W / W dispersion of a polyelectrolyte complex of cetyltrimethylammonium chloride (CTAC) and a copolymer of 80 parts by weight of acrylic acid, 10% by weight. Share hydroxyethyl acrylate and 10 parts by weight of methyl acrylate, neutralized with NaOH. The W / W dispersion of the polyelectrolyte complex was prepared by mixing the copolymer with the cationic surfactant in water. CTAC is added as a complexing agent. The mixture is stirred until a homogeneous emulsion is formed, then NaOH is added to stabilize the emulsion. The layer thickness of the layer of the polyelectrolyte complex on the oPP film was 3 μm. The oxygen barrier effect was measured at 50% relative humidity.

Oxygen permeability: 62 cm ³ (1 μm) / (m ² xdx bar)

EXAMPLE 3 IR Measurements for Demonstrating the Formation of Polyelectrolyte Complexes In a first experiment, polyacrylic acid (35% in water) and polyvinylamine (6.1% in water) in a mass ratio of 1: 1, 7 were mixed and stirred up. From the resulting solid reaction product, an IR spectrum was recorded. In the IR spectrum, the absorption of the NH vibrations (3300 cm ^-1 ) of the polyvinylamine disappeared and new absorptions of the carboxylation at 1530 cm ^-1 and 1390 cm ^-1 were formed. This indicates the formation of a polyelectrolyte complex.

In a second experiment, films of polyacrylic acid and of polyvinylamine were coated on top of one another in a ZnSe window in roughly the same mass ratio. From the double film, an IR spectrum was recorded in transmission and the difference spectrum of double film and polyvinylamine was formed. In the difference spectrum, the absorbances of the carboxylation at 1530 cm ^-1 and 1390 cm ^-1 are present and it shows a good agreement with the spectrum of the polyelectrolyte complex of the first experiment. This means that a polyelectrolyte complex has formed at the common interface of the two films of the double film.

Claims

claims

1. Use of at least one polyelectrolyte complex for imparting an oxygen barrier to packaging materials made of polymer films, wherein polymer structural components of the polyelectrolyte complex in polymerized form on the

Polymer film are applied and where

either at least one polymer film is coated on at least one side with an aqueous dispersion previously prepared by water-in-water emulsion polymerization or with a composition containing a polyelectrolyte complex previously prepared from anionic polymer and cationic surfactant,

or wherein a polymer film is coated on at least one side with at least three alternating layers, wherein each one of two adjacent layers contains at least one anionic polyelectrolyte constituent component and the other of two adjacent layers at least one cationic Polyelektrolytaufbaukomponente contains and at the mutual, adjacent interfaces of at least three alternating layers polyelectrolyte complexes can form.

2. Use according to the preceding claim, characterized in that the polyelectrolyte complex-containing layer is provided with a moisture protection.

3. Use according to the preceding claim, characterized in that the moisture protection is formed by coating with a polyolefin or by

Coextrusion of a polyolefin with at least one substance selected from polyelectrolyte complexes, anionic polyelectrolyte constituent components, and cationic polyelectrolyte constituent components.

4. Use according to one of the preceding claims, characterized in that the coating with the polyelectrolyte complex takes place in that (a1) the polymer film is provided on at least one side with a first coating which contains at least one anionic polymer,

(d) providing the second coating with a third coating containing at least one anionic polymer; or that

(a2) the polymer film is provided on at least one side with a first coating which contains at least one cationic substance selected from cationic surfactants and cationic polymers, (b2) providing the first coating with a second coating containing at least one anionic polymer, and

(c2) providing the second coating with a third coating containing at least one cationic substance selected from cationic surfactants and cationic polymers.

5. Use according to one of the preceding claims, characterized in that the anionic Polyelektrolytaufbaukomponente an anionic polymer is used which is selected from polymers which can be prepared from monomers selected from the group consisting of monoethylenically unsaturated C3- to Cio-carboxylic acids, vinylsulfonic acid , Styrenesulfonic acid, acrylamidomethylpropanesulfonic acid, vinylphosphonic acid and salts of these acids.

6. Use according to one of the preceding claims, characterized in that the cationic polyelectrolyte constituent component used is a cationic polymer which is selected from the group consisting of vinylimine azidium units containing polymers, polydiallyldimethylammonium halides, polymers containing vinylamine units, polymers containing ethyleneimine units, Dialkylaminoalkylacrylateinheiten containing polymers, containing Dialkylaminoalkylmethacrylateinheiten polymers, dialkylaminoalkylacrylamideinheiten containing polymers and Dialkylaminoalkylmethacryl- amide units containing polymers;

or that the cationic polyelectrolyte constituent component used is a cationic surfactant which is selected from the group consisting of compounds of the general formula

NMR ¹ R ² R ³ R ⁴ XH

where R 1 to R 4 independently of one another are alkyl groups each having 1 to 22 C atoms, where in each case at least one of the radicals R 1 to R 4 has at least 8 C atoms and X represents an anion.

7. Use according to one of the preceding claims, characterized in that the cationic polymer is a fully or partially hydrolyzed polyvinyl formamide and the anionic polymer is a homopolymer or a copolymer of acrylic acid or of methacrylic acid.

8. Use according to one of the preceding claims, characterized in that two coating compositions are applied simultaneously or in one step immediately after one another, wherein one of the coating compositions contains an anionic polymer and the other coating composition contains a cationic polymer.

9. Use according to any one of the preceding claims, characterized in that an aqueous dispersion prepared by water-in-water emulsion polymerization containing from 1 to 40% by weight of dispersed polyelectrolyte complex is used for coating with a polyelectrolyte complex.

10. Use according to one of the preceding claims, characterized in that the material of the polymer film is selected from polyethylene terephthalate, oriented polypropylene, polyethylene and biodegradable aliphatic-aromatic copolyesters.

1 1. A coated polymer film obtainable by use according to claim 1, characterized in that at least one side of the polymer film is coated with at least three alternating layers, wherein in each case one of two adjacent layers contains at least one anionic Polyelektrolytaufbaukomponen- te and the other of two adjacent layers at least one cationic Polyelektrolytaufbaukomponente contains and at the mutual, adjacent boundary surfaces of the at least three alternating layers form PoIy- electrolyte complexes.